*5.3. Research Limitations*

This study also has some limitations. On the one hand, this paper divided the land use functions into production, living and ecological functions, and used the subjective assigning method to assign and grade each function to distinguish the difference between strong and weak functions. However, compared with the current quantitative analysis model and method used by most scholars to study land use optimization, the method adopted in this article has strong subjectivity and cannot reflect the actual situation of the study area more objectively. Therefore, in order to improve the accuracy of land function identification, it is necessary to build a quantitative method or model to distinguish the strength difference of certain land functions in the future. On the other hand, this article only constructed an evaluation system of the PLES from the multifunctional perspective of land use. However, we treated other factors as attributes implicit in land use, such as socioeconomic development and terrain slope, which may lead to certain limitations in the recognition results. Thus, to better adapt to the new needs of land space planning and regional space governance in the future, it is necessary to comprehensively consider the regional natural geographical environment, resource endowments, social and economic development and regional policies and other factors to construct a more comprehensive evaluation system of the PLEF and further explore the formation mechanism of the regional the PLES.

#### **6. Conclusions**

(1) The land production function in Jiangjin District presents spatial differentiation characteristics that are high in the north and low in the south. The spatial distribution of the living function and production function showed obvious consistency. In addition, the ecological function of Jiangjin District was relatively dominant, and its spatial distribution showed significant spatial complementarity with the production function and living function distribution characteristics. Areas with high ecological functions are mainly distributed in the waters of the Yangtze River and mountainous areas. In general, the area dominated by living function and production function in the study area showed obvious spatial consistency, and the spatial distribution characteristics of ecological function dominance and production function dominance showed significant spatial complementarity. The spatial distribution pattern of the PLES conforms to the basic characteristics of the ecological barrier zone in the upper reaches of the Yangtze River and the overall requirements of achieving great protection and not engaging in large-scale development.

(2) The degree of coupling and coordination of the PLEF of Jiangjin District in 2018 can be divided into incongruous zone, break-in zone, and coordination zone. The coordination zone of the PLEF is mainly distributed in the northern part of Jiangjin District. The break-in zone of the PLEF is distributed in points between the imbalanced area and the coordination area, with a wide distribution range. The incongruous zone of the PLEF is distributed throughout Jiangjin District and is especially concentrated in the southern region. Moreover, the degree of coupling and coordination between every two of the PLEF generally shows spatial consistency—high in the north and low in the south.

(3) Four space categories can be identified in the study area: the PLEBS, the PLS, the PES, and the ES. The proportions of the four categories of space are 32.04%, 3.41%, 15.83%, and 48.72%. In general, the territorial spatial pattern of Jiangjin District presents the characteristics of the PLEBS and the ES as the main body, supplemented by the PLS and the PES.

(4) The optimized partitions of the PLES in Jiangjin District can be divided into four types: the ecological conservation area, the main production-living and ecological improvement zone, the main production-ecological and living improvement zone and comprehensive promotion zone. The space dominated by production and living functions should enhance the ecological function to realize the coordinated development of the PLES, while the ecological function-oriented space should take the protection of the ecological environment as the primary goal and exploit the advantages of the ecological function to develop ecotourism and ecological industries by protecting the ecological environment.

**Author Contributions:** The co-authors together contributed to the completion of this article. Specifically, it follows their individual contribution: conceptualization, H.C. and Q.Y.; validation, Q.Y. and K.S.; data curation, H.C., H.Z. and D.L.; formal analysis, Q.Y. and D.L.; methodology, H.C., K.S. and L.Z.; supervision, project administration, Q.Y.; writing—original draft, H.C.; writing—review and editing, H.C., Q.Y. and H.X.; visualization, H.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Chongqing Social Science Planning Project, grant number 2020YBZX15.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the author.

**Acknowledgments:** Thank you to everyone who contributed to this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
